Particle therapy, for example proton therapy, has been used for over 40 years to treat ocular melanoma.
Due to the specific nature of an eye and of ocular melanoma, particle therapy apparatus which are known for treating such diseases are generally making use of a dedicated single, anterior, and fixed beam line, with a dedicated nozzle having a small aperture. They use beam scattering techniques to deliver a broad beam for covering the target volume to be irradiated. A drawback of these apparatus is that dedicated equipment must be designed, manufactured, installed and operated, and that such dedicated apparatus cannot or can hardly be used for treating other types of tumors of a human body. A further drawback is that such apparatus may cause unwanted neutron and/or gamma ray radiation towards the patient because of the presence of beam scattering elements in the beamline and in the line of sight of the patient.
Another type of particle therapy apparatus for treating ocular melanoma is known from William F. Hartsell et al. in “Feasibility of Proton Beam Therapy for Ocular Melanoma Using a Novel 3D Treatment Planning Technique” (International Journal of Radiation Oncology*Biology*Physics, Volume 95, Issue 1, 1 May 2016, Pages 353-359, Particle Therapy Special Edition). This apparatus does not make use of a fixed beam line but rather makes use of a rotating gantry to direct the particle beam according to three different directions towards the target to be treated, so that the target will be irradiated with three different (generally coplanar) fields in the course of the treatment. A drawback of such apparatus is that it requires a relatively long treatment time, which is far from convenient for eye treatment and which also constitutes an economic disadvantage. Such apparatus also uses broad beam techniques to cover the target volume, such as the known wobbling technique for example. Hence, conformity of the actual received dose with a planned dose may not be optimal. Dose rates may also be insufficient with such techniques, which further impairs on treatment time.